In its 1968 yearly report, the Rockefeller Foundation acknowledged funding the development of so-called “anti-fertility vaccines” and their implementation on a mass-scale. From page 51 onward we read:

“(…) several types of drugs are known to diminish male fertility, but those that have been tested have serious problems of toxicity. Very little work is in progress on immunological methods, such as vaccines, to reduce fertility, and much more research is required if a solution is to be found here.”

The possibility of using vaccines to reduce male fertility was something that needed to be investigated further, according to the Rockefeller Foundation, because both the oral pill and the IUD were not suitable for mass-scale distribution.